First, I have a new (used) lens 50mm 1.4f Pentax. It seems to work fine at portrait distances, but won't focus to infinity. I had the same problem, but more pronounced, with a same/similar used lens at a local camera shop. We used a T42 to bayonet adapter and it would only focus very near. Their adapter was quite deep. (I think in affect it was what is called an extension tube) My adapter extends the lens only about 1mm. And the lens isn't a macro, it doesn't focus near any much beter than my f1:2.

Second, are there tests on high speed SD cards (like the Ultra II)?Are theyworth the extra $20 on the DS?

The adapter that you have, with its 1 mm flange, does not allow any lens to focus to infinity. I'm being kind when I say that they are worthless, unless you know how to disable the infinity focus stop on your lens so that it will go beyond its normal point. I have two of these, and was able to modify one old, cheap 400 mm preset lens to work alright, but the index mark is still shy of the 12 o'clock position.

The genuine Asahi Pentax adapters mount flush with the camera's mount, so there is not this problem with them. The Kalt adapters also work properly, but are harder to install and remove and come with a dedicated wrench to assist with this.

The adapter that you have, with its 1 mm flange, does not allow any lens to focus to infinity. I'm being kind when I say that they are worthless, unless you know how to disable the infinity focus stop on your lens so that it will go beyond its normal point. I have two of these, and was able to modify one old, cheap 400 mm preset lens to work alright, but the index mark is still shy of the 12 o'clock position.

The genuine Asahi Pentax adapters mount flush with the camera's mount, so there is not this problem with them. The Kalt adapters also work properly, but are harder to install and remove and come with a dedicated wrench to assist with this.

Just as a thought, you may have been using a 42mm T-mount adapter. These stick out past themount about 1/2" and are made to inf focus only with T-mount lenses. You may have been able to (partially) screw in your "Pentax" screw mount lens, but it will jam at some point as the thread pitch is different.

If you get one of the flush-fit M42 adapters, you should have no more problems, and in fact you can permanently leave it on the lens if you take off the little tab. This makes your lens a K-mount manual &amp; a lot handier to actually use, imho.